Application is made to establish a Clinical Science Group - Track A unit of the Adolescent Medicine HIV/AIDS Research Network for the purpose of planning and conducting research on the medical, biobehavioral, and psychosocial aspects of HIV and AIDS in adolescents. The subset of adolescents with HIV chosen for study are those teens 15 through 19 years of age who were infected through sexual behavior or as a consequence of injection drug use. For these youth a full study of spectrum of HIV disease and a descriptive study of behavior will be incorporated into a single base protocol. The base protocol will be designed to expand our limited understanding of the spectrum of HIV disease, progression, and co-morbidity during adolescence. Study of access to care, health care models, and health care utilization will enrich Network understanding of what constitutes optimal clinical care. Clinical management guidelines which merge understanding of both the biological and the behavioral characteristics of adolescents will be established and evaluated. Secondary protocols will be developed to explore, among other issues, the effects of maturation on mv transmission and infection, immune function, and clinical markers of HIV disease progression. The effect of HIV on development and neuropsychological function will be examined. The influence of patterns of adolescent behavior on health-promoting and risky activities will be considered. During Phase I (six months) collaborative activities with the Clinical Science Group will include the development of the clinical management guidelines, review and evaluate the base protocol, and help define the research agenda of the Network through the submission of research concepts. During Phase II, local research staff will be trained, study subjects recruited (20 HIV infected youth, l0 non-infected high risk teens), and the base protocol implemented. The Clinical Science Group will continue to expand the research agenda by protocol development and the evaluation of the clinical management guidelines.